Natasha Stacey fell to the ground and screamed when she learned her 11-year-old autistic son had escaped from a respite home and found his way to a duck pond, where he drowned.

Ms Stacey recalled how she felt yesterday after the Deputy Health and Disability Commissioner, Tania Thomas, ruled that the staff of the home were aware the boy, Julian, was at risk of escaping and the operators, Spectrum Care, had taken insufficient preventive action.

Although Julian was 11, he had the mind of a 2-year-old and needed constant supervision. He had made other escapes and attempted escapes, usually heading towards the main road.

But in February 2010, he left the backyard and found his way to the pond 250m away, where he drowned.

Speaking from her Auckland home yesterday, Ms Stacey said she had mixed emotions about the finding.

"The whole system failed Julian. They got too used to him. To me it seemed they got lazy."

Ms Stacey has a tattoo on her arm of Julian's face with the words 'Forever Mummy's Boy' - a constant reminder of her "bubbly child full of love".

She said Julian would not have been able to push a sequence of numbers on a keypad to open the respite home's gates unless he had been shown repeatedly how to do so.

Staff notes said that he loved water and the duck pond should be checked first if he wandered off.

Ms Thomas said that on the morning of February 7, 2010, a staff member checked that the backyard gates were secure before five children were taken on an outing.

When they returned, the gates were not rechecked, although the gate through which Julian might have left appeared closed.

He left during a period of reduced supervision while staff were carrying out a handover at 2.45pm.

When Ms Stacey arrived soon after to pick Julian up, staff told her he was missing and she joined in the search, fearing the worst.

When she returned to the property she heard an ambulance officer say his body had been found in the duck pond.

"I just fell to the ground. I just screamed. I broke down," she said through tears.

An apology she had received from the home was "too little too late".

Since Julian's death, Spectrum - which is contracted to the Ministry of Health - has made a number of security changes, including installing buzzers to alert staff when the gate is open and making a rear fence higher.

Spectrum spokesman Justin Walsh said he hoped Julian's death would be "a catalyst for change" for respite support services.

"We take our responsibility of care and support (in partnership with families) very seriously and initiated a wide-ranging internal investigation in the immediate aftermath."

Ms Stacey said family, including daughter Keyara, 7, were still struggling with Julian's death.